Window blind headrail



FIG. 1 is an end view of the design;

FIG. 2 is a bottom view of the design;

FIG. 3 is a right side view of the design;

FIG. 4 is a top view of the design;

FIG. 5 is an upper right perspective view of the design; and,

FIG. 6 is an upper left perspective view of the design.

The window blind headrail has been shown broken away in order to indicate that a specific length of window blind headrail forms no part of the claimed design. The broken line defining the breakaway also forms no part of the claimed design. 

The ornamental design for a window blind headrail, as shown and described. 